| # |
제출 시각 |
아이디 |
문제 |
언어 |
결과 |
실행 시간 |
메모리 |
| 19433 |
2016-02-24T12:29:12 Z |
emppu |
Ω (kriii4_P3) |
C++14 |
|
0 ms |
1724 KB |
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <cstring>
#include <cassert>
#include <algorithm>
#include <vector>
#include <string>
#include <set>
#include <map>
#include <queue>
#include <deque>
#include <list>
#include <bitset>
#include <tuple>
using namespace std;
#define f0(_X,_Y) for(int (_X)=0;(_X)<(_Y);++(_X))
#define f1(_X,_Y) for(int (_X)=1;(_X)<=(_Y);++(_X))
#define ff(_X,_Y,_Z) for(int (_X)=(_Y);(_X)<=(_Z);++(_X))
#define fF(_X,_Y,_Z) for(int (_X)=(_Y);(_X)<(_Z);++(_X))
#define rf0(_X,_Y) for(int _X=(_Y)-1;(_X)>=0;--(_X))
#define rf1(_X,_Y) for(int _X=(_Y);(_X)>0;--(_X))
#define rff(_X,_Y,_Z) for(int _X=(_Y);(_X)>=(_Z);--(_X))
#define rfF(_X,_Y,_Z) for(int _X=(_Y);(_X)>(_Z);--(_X))
#define PRT(_X) std::cout<< #_X ": "<<_X<<std::endl;
#define scan1(_X) scanf("%d",&_X);
#define scan2(_X,_Y) scanf("%d%d",&_X,&_Y);
#define scan3(_X,_Y,_Z) scanf("%d%d%d",&_X,&_Y,&_Z);
#define define1(_1) int _1; scan1(_1)
#define define2(_1,_2) int _1,_2; scan2(_1,_2)
#define define3(_1,_2,_3) int _1,_2,_3; scan3(_1,_2,_3)
#define EXPAND(_1) _1
#define SELECT(_1,_2,_3,_4,NAME,...) NAME
#define scan(...) EXPAND(SELECT(__VA_ARGS__, scan4, scan3, scan2, scan1)(__VA_ARGS__))
#define define(...) EXPAND(SELECT(__VA_ARGS__, define4, define3, define2, define1)(__VA_ARGS__))
#define print(_X) printf("%d\n",_X)
#define PAIR_STRUCT(_T,_X,_Y,...) struct _T{int _X,_Y,##__VA_ARGS__; bool friend operator < (const _T &p, const _T &q){if(p._X!=q._X) return p._X<q._X; return p._Y<q._Y;}}
typedef long long ll;
const int MOD = 1000000007;
ll a[103];
ll d[103];
ll inv(ll a, ll b=MOD)
{
ll s = 0; ll old_s = 1;
ll r = b; ll old_r = a;
while (r!=0)
{
ll quotient = old_r / r;
tie(old_r, r) = make_tuple(r, old_r - quotient * r);
tie(old_s, s) = make_tuple(s, old_s - quotient * s);
}
ll inv = old_s%MOD;
if(inv<0) inv += MOD;
return inv;
}
int main()
{
ll p,q,n,k;
scanf("%lld%lld%lld%lld",&p,&q,&n,&k);
ll Pl = q*inv(p)%MOD;
ll Pr = (p-q)*inv(p)%MOD;
if(n==1)
{
if(k==0) print(0); else print(1);
}
else if(n==2)
{
printf("%lld\n",Pr);
}
else
{
a[1] = 1;
a[2] = inv(Pr);
ff(i,2,n-2) // d_i = a[i] d_1
{
// d[i] = Pl d[i-1] + Pr d[i+1]
// d[i+1] = (a[i] - Pl a[i-1] )/Pr d_1
a[i+1] = (a[i]-Pl*a[i-1]%MOD)*inv(Pr)%MOD;
if(a[i+1]<0) a[i+1] += MOD;
}
// d[n-1] = a[n-1] d_1
// d[n-1] = Pl a[n-2] d_1 + Pr
// d_1 = Pr / (a[n-1]-Pl a[n-2])
d[1] = Pr * inv(a[n-1]-Pl*a[n-2]%MOD) % MOD;
if(d[1]<MOD) d[1] += MOD;
printf("%lld\n",d[1]*a[k]%MOD);
}
return 0;
}
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
0 ms |
1724 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
